JP6541683B2 - Molded article for polishing layer and polishing pad - Google Patents

Description

  The present invention relates to a molded body for a polishing layer used as a polishing layer of a polishing pad for polishing a semiconductor wafer, a semiconductor device, a silicon wafer, a hard disk, a glass substrate, an optical product, or various metals.

  Chemical mechanical polishing (CMP) is known as a polishing method used to mirror-finish a semiconductor wafer or to planarize the surface of an insulating film or a conductor film of a semiconductor device. The CMP is a method of polishing the surface of a material to be polished such as a wafer with a polishing pad using a polishing slurry (hereinafter, also simply referred to as a slurry) containing abrasive grains and a reaction solution.

  Conventionally, a non-woven fabric type polishing pad has been widely used as a polishing pad for CMP. The non-woven type polishing pad is a flexible polishing pad comprising a non-woven fabric impregnated with polyurethane. The non-woven fabric type polishing pad is also flexible and has an advantage in that it has good contact with the material to be polished. In addition, since there is a void in the non-woven fabric, there is an advantage that the retention of the slurry is good. On the other hand, the non-woven fabric type polishing pad has a disadvantage that its ability to flatten the surface to be polished (referred to as planarization) is low because it is flexible. In addition, the non-woven fabric type polishing pad also has a defect that the surface to be polished is easily scratched when the non-woven fabric is clogged with abrasive grains or polishing debris. Furthermore, when the abrasive grains and polishing debris have penetrated deep into the gaps of the non-woven fabric, they can not be sufficiently removed by washing, which results in a short life.

  As a polishing pad of a type different from the non-woven fabric type polishing pad, a polishing pad mainly composed of a polymer foam is also known. A polishing pad mainly composed of a polymer foam has superior rigidity because it has high rigidity as compared with a non-woven fabric type polishing pad. In addition, since the polishing pad mainly composed of a polymer foam has a closed cell structure, abrasive grains and polishing debris do not penetrate deep into the void as in the non-woven fabric type polishing pad. Therefore, the life is relatively long because the removal of abrasive grains and polishing debris is relatively easy by cleaning. As a polishing pad mainly composed of a polymer foam, for example, polishing is provided as a polishing layer is a foamed polyurethane molded body obtained by casting foam molding of a two-component curing type polyurethane as disclosed in Patent Documents 1 to 6 below. Pads are known. Moreover, the polishing pad provided with a thermoplastic foam polyurethane molded object as a polishing layer as shown to the following patent document 7 is also known.

  Integrated circuits are highly integrated and multilayered in semiconductor devices. A polishing pad used for planarization of semiconductor devices is required to have higher planarization. The highly planarizing polishing pad has a high polishing rate of a portion to be polished and a low polishing rate of a portion not to be polished. High hardness is required for a polishing pad with high planarization. A polishing pad provided with a foamed polyurethane molding as a polishing layer has high flatness because the hardness of the polishing layer is relatively high.

  In recent years, with the further high integration and multilayer wiring of semiconductor devices, a polishing pad having even higher flatness is required. In the case of using a polishing pad provided with a foamed polyurethane molded product as a polishing layer, it has been difficult to realize high planarization by further increasing the hardness of the polishing layer. In order to provide a polishing pad having even higher flatness, for example, the following Patent Documents 8 and 9 disclose a high hardness polishing pad provided with a nonporous thermoplastic polyurethane molded body as a polishing layer.

Unexamined-Japanese-Patent No. 2000-178374 Unexamined-Japanese-Patent No. 2000-248034 JP 2001-89548 A JP-A-11-322878 JP, 2002-371154, A International Publication No. 2007/034980 JP 2004-35669 A JP 2014-038916 A JP, 2009-101487, A

  In the case of a polishing pad provided with a conventional nonporous thermoplastic polyurethane molded article as a polishing layer, it has been difficult to achieve both high moldability and high flatness.

  An object of the present invention is to provide a molded article for an abrasive layer having both high moldability and high flatness.

  One aspect of the present invention is a polymer diol, an organic diisocyanate, a first chain extender containing a diol having 4 or less carbon atoms, and a second chain extender containing a diol having 5 or more carbon atoms. A non-porous abrasive layer comprising a thermoplastic polyurethane which is a polymer of a monomer containing at least one of nitrogen and a nitrogen content of 6.3 to 7.4% by mass derived from the isocyanate group of the organic diisocyanate. It is a molded object. The above-mentioned thermoplastic polyurethanes have high moldability. In addition, since the non-porous thermoplastic polyurethane molded article has high hardness, it exhibits high flatness when used as an abrasive layer.

  In addition, as a first chain extender, ethylene glycol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 2,3-butanediol, 1,4-butanediol, 2- The second chain extender comprises at least one member selected from the group consisting of methyl-1,3-propanediol, and the second chain extender is 1,5-pentanediol, 2,2-dimethylpropane-1,3-diol, 3- Methyl 1,5-pentanediol, 1,6-hexanediol, cyclohexanediol, 1,8-octanediol, cyclohexanedimethanol, 1,9-nonanediol, 2-methyl-1, 8-octanediol, and 1, It is preferable to include at least one selected from the group consisting of 10-decanediol.

  In addition, the thermoplastic polyurethane has an endothermic peak by differential scanning calorimetry (DSC) at 185 ° C. or less, and the crystallization enthalpy (ΔH) determined from the endothermic peak area at the endothermic peak is 2 to 15 J / g. Is preferable from the viewpoint that moldability is particularly excellent.

  Moreover, when the difference of a carbon number of mutual mutually contains 2 or more, when it contains the 1st chain extender and 2nd chain extender, it is preferable from the point which a moldability is especially excellent.

Further, a molded body for a polishing layer is preferable in the case of having a density of 1.0 g / cm ³ or more and a JIS-D hardness of 75 or more from the viewpoint of particularly excellent flatness.

  When the abrasive layer molding has a surface having a contact angle with water of 75 degrees or less, it is preferable in that scratching is less likely to occur on the surface to be polished.

  In addition, in the case where the thermoplastic polyurethane has a tensile elastic modulus at 50 ° C. of 250 to 1500 MPa when saturated and swollen with warm water of 50 ° C., it is possible to obtain an abrasive layer capable of maintaining high hardness to the extent that scratch does not occur. It is preferable from

  The thermoplastic polyurethane has the following formula: A / B × 100 (A is a storage elastic modulus at 50 ° C. when saturated swelling with warm water at 50 ° C., B is a saturated elastic swelling with warm water at 50 ° C. When the water saturated swelling retention ratio of the storage elastic modulus, which is calculated from the storage elastic modulus at 50 ° C., is 55% or more, it is preferable from the viewpoint that the polishing characteristics are unlikely to change with time during polishing.

  When the high molecular weight diol contains at least one selected from the group consisting of polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and polymethyltetramethylene glycol, it is preferable from the viewpoint of excellent hydrophilicity.

  In addition, when the abrasive layer molding includes a polishing surface having a recess, and the recess has a tapered corner portion that spreads toward the polishing surface, burrs are less likely to occur at the corner of the recess during polishing. It is preferable from the point of view.

  Another aspect of the present invention is a polishing pad including any of the above-described abrasive layer moldings as a polishing layer. According to such a polishing pad, polishing excellent in polishing uniformity can be realized.

  In addition, in the case where a cushion layer having a hardness lower than the hardness of the polishing layer is laminated, the global planarization (overall planarization) and the local planarization (local planarization) can be obtained. It is preferable from the point which the polishing pad excellent in balance is obtained.

  ADVANTAGE OF THE INVENTION According to this invention, while it is excellent in a moldability, the molded object for abrasive layers which expresses high planarization property when it uses as an abrasive layer is obtained.

FIG. 1 is a scanning electron microscope (SEM) photograph showing an example of a burr generated at a corner of a recess of a polishing layer. FIG. 2 is a scanning electron microscope (SEM) photograph showing an example of a groove having a tapered corner portion spreading toward the polishing surface in the polishing layer of the polishing pad. FIG. 3 is an explanatory view for explaining CMP using the polishing pad of the present embodiment.

  Hereinafter, the molded body for a polishing layer and the polishing pad according to one embodiment of the present invention will be described in detail.

  The molded article for a polishing layer according to the present embodiment includes a polymer diol, an organic diisocyanate, a first chain extender containing a diol having 4 or less carbon atoms, and a second chain containing a diol having 5 or more carbon atoms. A polymer of a monomer containing an extender, and comprising a thermoplastic polyurethane having a nitrogen content of 6.3 to 7.4% by mass derived from the isocyanate group of the organic diisocyanate, and is nonporous It is a thermoplastic polyurethane molded article.

  As high molecular weight diol, polyether diol, polyester diol, polycarbonate diol etc. are mentioned, for example.

  Examples of polyether diols include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polymethyltetramethylene glycol, polyoxypropylene glycol, glycerin-based polyalkylene ether glycol and the like. These may be used alone or in combination of two or more.

  Examples of polyester diols include those obtained by direct esterification reaction or transesterification reaction of ester forming derivatives such as dicarboxylic acids or their esters, anhydrides and the like and low molecular weight diols.

  Specific examples of the dicarboxylic acid include oxalic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, 2-methylsuccinic acid, 2-methyladipic acid, 3- Aliphatic dicarboxylic acids having 2 to 12 carbon atoms such as methyladipic acid, 3-methylpentanedioic acid, 2-methyloctanedioic acid, 3,8-dimethyldecanedioic acid, 3,7-dimethyldecanedioic acid; triglycerides Aliphatic dicarboxylic acids such as a dimerized aliphatic dicarboxylic acid having 14 to 48 carbon atoms (dimer acid) obtained by fractional distillation and dimerized unsaturated fatty acid (dimer acid) and hydrogenated products thereof (hydrogenated dimer acid); 1,4 -Alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid; and aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid and orthophthalic acid. Examples of the dimer acid and hydrogenated dimer acid include trade names "Puripol 1004", "Pripol 1006", "Pripol 1009", "Pripol 1013" and the like manufactured by Unichema. These may be used alone or in combination of two or more.

  Further, specific examples of the low molecular weight diol include, for example, ethylene glycol, 1,3-propanediol, 1,2-propanediol, 2-methyl-1,3-propanediol, 1,4-butanediol, neopentyl glycol 1,1,5-Pentanediol, 3-Methyl-1,5-Pentanediol, 1,6-Hexanediol, 1,7-Heptanediol, 1,8-Octanediol, 2-Methyl-1,8-Octanediol And aliphatic diols such as 1,9-nonanediol and 1,10-decanediol; and alicyclic diols such as cyclohexanedimethanol and cyclohexanediol. These may be used alone or in combination of two or more. Among these, diols having 6 to 12 carbon atoms, and further diols having 8 to 10 carbon atoms, particularly diols having 9 carbon atoms are preferable.

  As polycarbonate diol, what is obtained by making a carbonate compound and low molecular weight diol react is mentioned.

  Specific examples of the carbonate compound include dialkyl carbonates such as dimethyl carbonate and diethyl carbonate, alkylene carbonates such as ethylene carbonate, and diaryl carbonates such as diphenyl carbonate. Moreover, as low molecular weight diol, the low molecular weight diol similar to what was mentioned above is mentioned. These may be used alone or in combination of two or more.

  The high molecular weight diols may be used alone or in combination of two or more. Among these, it is particularly preferable to contain at least one selected from polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and polymethyltetramethylene glycol or their derivatives, from the viewpoint of excellent hydrophilicity.

  The number average molecular weight of the high molecular weight diol is not particularly limited, but is preferably 600 to 1,400, more preferably 600 to 1,200, and particularly preferably 600 to 1,000. When the number average molecular weight of the high molecular weight diol is too low, the hardness and the tensile modulus of elasticity tend to decrease, and the flatness of the polishing layer tends to decrease. On the other hand, when the number average molecular weight of the polymer diol is too high, a thermoplastic polyurethane molded article with low resilience and high toughness can be easily obtained. Abrasive layers that use low-resilience, high-toughness thermoplastic polyurethane moldings tend to have burrs during polishing at the corners (edges and shoulders) of the recess when the recess is formed on the surface. is there. The number average molecular weight of the high molecular weight diol is a value calculated based on the hydroxyl value measured in accordance with JIS K 1557.

  Examples of organic diisocyanates include ethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, 2,2,4- or 2,4,4'-trimethylhexamethylene diisocyanate, dodecamethylene diisocyanate, isophorone diisocyanate, isopropylidene bis. (4-cyclohexylisocyanate), cyclohexylmethane diisocyanate, methylcyclohexane diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, lysine diisocyanate, 2,6-diisocyanatomethylcaproate, bis (2-isocyanatoethyl) fumarate, bis ( 2-isocyanatoethyl) carbonate, 2-isocyanatoethyl-2,6-diisocyanatohexanoate, cyclohexylene diisocyanate Aliphatic or cycloaliphatic diisocyanates such as methylcyclohexylene diisocyanate, bis (2-isocyanatoethyl) -4-cyclohexene; 2,4'- or 4,4'-diphenylmethane diisocyanate, 2,4- or 2,6- Tolylene diisocyanate, m- or p-phenylene diisocyanate, m- or p-xylylene diisocyanate, 1,5-naphthyl diisocyanate, 4,4'-diisocyanatobiphenyl, 3,3-dimethyl-4,4'- Examples thereof include aromatic diisocyanates such as diisocyanatobiphenyl, 3,3-dimethyl-4,4'-diisocyanatodiphenylmethane, chlorophenylene-2,4-diisocyanate and tetramethyl xylylene diisocyanate. These may be used alone or in combination of two or more. Among these, at least one selected from 4,4'-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate and isophorone diisocyanate, in particular, 4,4'-diphenylmethane diisocyanate is resistant to It is preferable from the point which the abrasive layer which is excellent in abrasion resistance is obtained.

  The monomer used for the polymerization of the thermoplastic polyurethane contains a first chain extender which is a diol having 4 or less carbon atoms and a second chain extender which is a diol having 5 or more carbon atoms. . When only a diol having 4 or less carbon atoms is used as a chain extender, hydrogen bonds between -NH and -CO groups in the molecular chain are increased to form a dense network structure, thereby achieving high hardness and high hardness. It becomes easy to obtain a thermoplastic polyurethane having strength. On the other hand, the melting point and the crystallinity increase, and the moldability of the thermoplastic polyurethane decreases. When a diol having 4 or less carbon atoms and a diol having 5 or more carbon atoms are used in combination as a chain extender, the distance between the ester and the urethane group becomes long, and the aggregation density between molecular chains is appropriately reduced. The crystallinity is lowered to obtain a thermoplastic polyurethane excellent in moldability.

  Specific examples of the first chain extender which is a diol having 4 or less carbon atoms include, for example, a diol having 2 carbon atoms such as ethylene glycol; a diol having 3 carbon atoms such as 1,3-propanediol; Examples thereof include butanediol such as butanediol, 1,3-butanediol, 2,3-butanediol and 1,4-butanediol, and diol having 4 carbon atoms such as 2-methyl-1,3-propanediol.

  Further, as the second chain extender which is a diol having 5 or more carbon atoms, for example, a diol having 5 carbon atoms such as 1,5-pentanediol or 2,2-dimethylpropane-1,3-diol; 3- Diols having 6 carbon atoms such as methyl 1,5-pentanediol, 1,6-hexanediol, cyclohexanediol; diols having 8 carbons such as 1,8-octanediol, cyclohexanedimethanol; 1,9-nonanediol, Examples thereof include C9 diols such as 2-methyl-1,8-octanediol; and C10 diols such as 1,10-decanediol.

  The content ratio of the first chain extender, which is a diol having 4 or less carbon atoms, and the second chain extender, which is a diol having 5 or more carbon atoms, is not particularly limited, and is adjusted according to the balance between moldability and hardness. Be done. Preferably, for example, it is preferable to blend 0.09 to 0.67 mole, more preferably 0.25 to 0.54 mole, of the second chain extender with respect to 1 mole of the first chain extender. If the proportion of the second chain extender is too low, the effect of improving the moldability of the thermoplastic polyurethane tends to be insufficient. If the proportion of the second chain extender is too high, the hardness of the thermoplastic polyurethane tends to decrease.

  In addition, the first chain extender, which is a diol having 4 or less carbon atoms, and the second chain extender, which is a diol having 5 or more carbon atoms, have a difference of 2 or more carbon atoms in particular, particularly in the formability It is preferable from the point which can obtain the outstanding thermoplastic polyurethane.

  As a chain extender used for the polymerization of thermoplastic polyurethane, in addition to the first chain extender and the second chain extender, conventionally used for the polymerization of thermoplastic polyurethane as long as the effects of the present invention are not impaired. A low molecular weight compound having two or more active hydrogen atoms capable of reacting with an isocyanate group in the molecule may be further used in combination.

  The compounding ratio of each component of the polymeric diol, chain extender and organic diisocyanate used for the polymerization of the thermoplastic polyurethane is appropriately selected in consideration of the physical properties such as the desired abrasion resistance. Specifically, for example, an isocyanate group contained in the organic diisocyanate is 0.95 to 1.3 mol, further preferably 0.96 to 1 per 1 mol of active hydrogen atoms contained in the polymer diol and the chain extender. It is preferable that the ratio is 10 mol, particularly 0.97 to 1.05 mol from the viewpoint of the mechanical strength and abrasion resistance of the thermoplastic polyurethane, the productivity of the thermoplastic polyurethane and the storage stability. If the proportion of isocyanate groups is too low, the mechanical strength and the abrasion resistance of the thermoplastic polyurethane molded article tend to be reduced. When the proportion of isocyanate groups is too high, the productivity and storage stability of the thermoplastic polyurethane tend to be reduced.

  The mass ratio of the polymeric diol, the organic diisocyanate and the chain extender is as follows: amount of polymeric diol / (amount of organic diisocyanate and chain extender) = 15/85 to 45/55, and further 20/80 to 40 / It is preferably 60, in particular 25/75 to 35/65.

  The thermoplastic polyurethane comprises a polymeric diol, an organic diisocyanate, a first chain extender comprising a diol having 4 or less carbon atoms, and a second chain extender comprising a diol having 5 or more carbon atoms It is obtained by polymerizing a monomer by a urethanation reaction using a known prepolymer method or one shot method. Preferably, using a single screw or multi-screw extruder, continuous melt polymerization is carried out with the monomers being melt mixed substantially in the absence of a solvent.

  The nitrogen content ratio derived from organic diisocyanate in the thermoplastic polyurethane is 6.3 to 7.4% by mass, 6.5 to 7.3% by mass, further 6.7 to 7.3% by mass Is preferred. By adjusting the nitrogen content ratio derived from the isocyanate group of the organic diisocyanate to 6.3 to 7.4% by mass, a thermoplastic polyurethane having high hardness can be obtained because the amount of hard segment in the polyurethane becomes high. When the nitrogen content ratio derived from organic diisocyanate is less than 6.3% by mass, the hardness of the thermoplastic polyurethane is lowered, and the planarization property and the polishing efficiency of the resulting polishing layer are reduced. In addition, when the nitrogen content ratio derived from organic diisocyanate exceeds 7.4% by mass, the hardness of the thermoplastic polyurethane becomes too high, so that the polishing layer is apt to easily generate a scratch on the surface to be polished.

  The thermoplastic polyurethane is preferably an endothermic peak temperature obtained by differential scanning calorimetry (DSC) of 185 ° C. or less, and more preferably 180 ° C. or less from the viewpoint of excellent formability. The lower limit is not particularly limited, but is preferably about 160 ° C., and more preferably about 170 ° C. In addition, the crystallization enthalpy (ΔH) determined from the endothermic peak area at the endothermic peak is preferably 2 to 15 J / g, and more preferably 5 to 11 J / g from the viewpoint of particularly excellent formability.

  The thermoplastic polyurethane preferably has a contact angle with water of 75 degrees or less, more preferably 70 degrees or less, and particularly preferably 65 degrees or less. When the contact angle with water is too high, there is a tendency to obtain an abrasive layer which is apt to cause scratches on the surface to be polished.

  Furthermore, the hardness of the thermoplastic polyurethane is preferably 75 or more, more preferably 80 or more in JIS-D hardness. When the JIS-D hardness is too low, there is a tendency to obtain a polishing layer having low local planarization because the followability to the surface to be polished is high.

The density of the thermoplastic polyurethane molded body is preferably 1.0 g / cm ³ or more, more preferably 1.1 g / cm ³ or more, and particularly preferably 1.2 g / cm ³ or more. If the density of the thermoplastic polyurethane molded article is too low, an abrasive layer with low local planarization tends to be obtained.

  The thermoplastic polyurethane preferably has a tensile elastic modulus at 50 ° C. of 250 to 1,500 MPa, more preferably 400 to 1,300 MPa, and particularly preferably 600 to 1,000 MPa after saturated swelling with water at 50 ° C. If the tensile elastic modulus at 50 ° C. after saturated swelling with water at 50 ° C. is too low, the polishing layer tends to be softened during polishing and the planarization and the polishing efficiency may be reduced. In addition, when the tensile elastic modulus at 50 ° C. after saturated swelling with water at 50 ° C. is too high, there is a tendency for the scratch to be easily generated on the surface to be polished.

The thermoplastic polyurethane has a formula (1): A / B × 100
(A: storage elastic modulus at 50 ° C. when saturated swelling with 50 ° C. warm water, B: storage elastic modulus at 50 ° C. when not saturated swelling with 50 ° C. hot water) (1)
It is preferable that the water-saturated swelling retention of storage elastic modulus calculated by the above is 55% or more, more preferably 60% or more, and particularly preferably 75% or more. When the retention rate at the time of water saturation swelling of the storage elastic modulus is too low, the characteristic change of the polishing layer due to moisture is large, for example, the polishing speed when the polishing pad is left in a wet state for several hours to several days after polishing is completed. Tend to decrease.

  In addition, the storage elastic modulus at 50 ° C. when not saturated and swollen means that the test piece was conditioned by leaving it for 3 days at 23 ° C. and 65% RH without saturated swelling with warm water of 50 ° C. Storage modulus at 50 ° C. measured immediately after. The storage elastic modulus at 50 ° C. when not saturated and swollen is preferably 600 to 1900 MPa, and more preferably 800 to 1700 MPa. When the storage elastic modulus at 50 ° C. is too low, the polishing uniformity tends to decrease, and when it is too high, scratching tends to increase.

  The thermoplastic polyurethane molded article of the present embodiment is a non-porous (non-foaming) molded article. Such non-porous thermoplastic polyurethane molded articles exhibit high flatness when used as an abrasive layer due to their high hardness. Such non-porous thermoplastic polyurethane molded articles can be produced as a sheet by extruding or injection molding thermoplastic polyurethane containing no components such as a foaming agent using a T-die. preferable. In particular, a sheet obtained by extrusion using a T-die is preferable because a sheet having a uniform thickness can be obtained.

  The thickness of the molded body for polishing layer is not particularly limited, and may be appropriately adjusted according to the layer configuration and use of the polishing pad. Specifically, it is preferably 1.5 to 3.0 mm, more preferably 1.7 to 2.8 mm, and particularly preferably 2.0 to 2.5 mm.

  The polishing pad according to the present embodiment further has a cushion layer laminated on the polishing layer formed of the polishing layer molding, even if it is a single-layer type polishing pad using the polishing layer molding having the predetermined shape as it is. It may be a multilayer polishing pad.

  The cushion layer is preferably a layer having a hardness lower than that of the polishing layer. When the hardness of the cushioning layer is lower than the hardness of the polishing layer, the hard polishing layer easily follows the local unevenness of the surface to be polished, so warpage or waviness of the entire material to be polished can be achieved. In order to follow the cushion layer, it is possible to realize polishing having an excellent balance between global planarization and local planarization.

  Specific examples of the material used as the cushion layer include a composite obtained by impregnating polyurethane with a known non-woven fabric; rubber such as natural rubber, nitrile rubber, polybutadiene rubber, silicone rubber, etc .; polyester thermoplastic elastomer, polyamide thermoplastic elastomer And thermoplastic elastomers such as fluorine-based thermoplastic elastomers; foamed plastics; polyurethanes and the like. Among these, polyurethane having a foam structure is particularly preferable in that the flexibility is appropriate.

  The thickness of the cushion layer is not particularly limited, but is preferably, for example, about 0.3 to 1.2 mm, and more preferably about 0.5 to 1.0 mm. If the cushion layer is too thin, the effect of following the entire material to be polished on warpage and waviness tends to decrease, and the global planarization of the polishing pad tends to decrease. On the other hand, when the cushion layer is too thick, the entire polishing pad tends to be soft and difficult to perform stable polishing.

  In the molded body for an abrasive layer of the present embodiment, usually, concave portions such as grooves or holes are formed concentrically, for example, concentrically in order to supply the slurry uniformly and sufficiently to the polishing surface. Such a recess also serves to discharge polishing debris that may cause scratching and to prevent wafer breakage due to adsorption of the polishing pad.

  The method for forming the recess in the polishing surface is not particularly limited. For example, the surface of the molded abrasive layer is cut to form a predetermined pattern of recesses, or the recesses are formed by transfer with a mold during injection molding, or stamped with a heated mold. And the like.

  For example, when the grooves are formed concentrically, the distance between the grooves is preferably about 2.0 to 50 mm, more preferably 5.5 to 30 mm, and particularly preferably about 6.0 to 15 mm. The width of the groove is preferably about 0.1 to 3.0 mm, and more preferably about 0.4 to 2.0 mm. The depth of the groove is preferably 0.2 to 1.8 mm, and more preferably 0.4 to 1.5 mm. Moreover, as a cross-sectional shape of a groove | channel, shapes, such as a rectangle, a trapezoid, a triangle, a semicircle, etc. are suitably selected according to the objective, for example.

  When a recess is formed on the polishing surface of the abrasive layer molding, the material to be polished or the conditioner comes in contact with the corner portion (shoulder portion, end portion) of the recess repeatedly for a long time, as shown in FIG. Burr may occur. Such burrs gradually close the recess and gradually reduce the amount of slurry supplied. As a result, the polishing speed and the polishing uniformity are gradually reduced. In such a case, as shown in FIG. 2, it is preferable to form a tapered corner portion having a cut-out cross section in at least one corner portion of the recess. Such a tapered corner portion is a surface inclined with respect to the direction perpendicular to the polishing surface. By forming such a tapered shape in at least one corner portion of the recess, it is difficult to generate burrs that close the recess even when used for polishing for a long time.

  One embodiment of CMP using a polishing pad including the molded body for a polishing layer of the present embodiment as a polishing layer will be described. In CMP, for example, a CMP apparatus 20 including a circular rotary surface plate 11 as shown in FIG. 3, a slurry supply nozzle 12, a carrier 13, and a pad conditioner 14 is used. The polishing pad 10 is attached to the surface of the rotary surface plate 11 with a double-sided tape or the like. Further, the carrier 13 supports the material 15 to be polished.

  In the CMP apparatus 20, the rotary surface plate 11 is rotated in the direction indicated by the arrow by a motor (not shown). Further, the carrier 13 is rotated, for example, in a direction indicated by an arrow by a motor (not shown) in the plane of the rotary surface plate 11. The pad conditioner 14 is also rotated, for example, in the direction indicated by the arrow by a motor (not shown) in the plane of the rotary surface plate 11.

  First, while the distilled water is being flowed, the rotating pad conditioner 14 is pressed against the polishing surface of the polishing layer of the polishing pad 10 fixed and rotating on the rotary surface plate 11 to condition the polishing surface. As the pad conditioner, for example, a conditioner in which diamond particles are fixed to the support surface by nickel electrodeposition or the like is used. Thus, the polishing surface is adjusted to a surface roughness suitable for polishing the surface to be polished. Next, the polishing slurry 16 is supplied from the slurry supply nozzle 12 to the surface of the rotating polishing pad 10. The polishing slurry 16 is, for example, a liquid medium such as water or oil; an abrasive such as silica, alumina, cerium oxide, zirconium oxide or silicon carbide; a base, an acid, a surfactant, an oxidizing agent, a reducing agent, a chelating agent, etc. contains. In addition, when performing CMP, a lubricating oil, a coolant and the like may be supplied together with the polishing slurry, if necessary. Then, the material to be polished 15 fixed to the carrier 13 and rotated is pressed against the polishing surface of the polishing pad 10 uniformly wetted by the polishing slurry 16. Then, the polishing process is continued until a predetermined flatness is obtained. By adjusting the pressing force applied during polishing and the speed of relative movement between the rotary surface plate 11 and the carrier 13, the finished quality is affected.

  The polishing conditions are not particularly limited, but in order to perform efficient polishing, it is preferable that the rotational speed of each of the platen and the substrate be as low as 300 rpm or less. Further, the pressure applied to the substrate is preferably 150 kPa or less in order to suppress the occurrence of scratches. In addition, it is preferable to continuously supply the polishing slurry to the polishing surface while polishing. The supply amount of the polishing slurry is preferably such that the entire polishing surface is always wet with the polishing slurry.

  The CMP of the present embodiment is preferably used for polishing in manufacturing processes of various semiconductor devices and MEMS (Micro Electro Mechanical Systems). Specific examples of the material to be polished include, for example, silicon wafers, semiconductor wafers such as silicon oxide and silicon oxide fluoride; and inorganic materials such as silicon oxide films, glass films and silicon nitride films formed on a wiring board having a predetermined wiring. Insulating film: Film mainly containing polysilicon, aluminum, copper, titanium, titanium nitride, tungsten, tantalum, tantalum nitride etc. Optical glass such as photomask, lens, prism etc. Inorganic conductive film such as tin-doped indium oxide (ITO) Optical integrated circuits composed of glass and crystalline materials, optical switching devices, optical waveguides, end faces of optical fibers, optical single crystals such as scintillators; solid laser single crystals; sapphire substrates for blue laser LEDs; silicon carbide, phosphide Semiconductor single crystals such as gallium and gallium arsenide; Glass substrates for magnetic disks; De like; methacrylic resins and synthetic resins such as polycarbonate resin.

  Hereinafter, the present invention will be more specifically described by way of examples. The scope of the present invention is not limited to these examples.

Example 1
Polytetramethylene glycol (PTMG850) having a number average molecular weight of 850, 1,4-butanediol (BD) which is a chain extender of 4 carbon atoms, 3-methyl 1,5-pentanediol which is a chain extender of 6 carbon atoms (MPD), and a unit amount of 4,4'-diphenylmethane diisocyanate (MDI) mixed in a ratio of PTMG 850: BD: MPD: MDI = 19.0: 14.7: 6.4: 59.9 (mass ratio) I prepared my body. Then, a monomer was continuously supplied to a twin-screw extruder by a metering pump and continuously melt-polymerized while being kneaded to obtain a polymer. After continuously extruding the strand of the polymer in the molten state continuously discharged from the twin-screw extruder into water, pellets of thermoplastic polyurethane A were obtained by shredding with a pelletizer. And thermoplastic polyurethane A was evaluated by the following evaluation methods.

<Measurement of nitrogen content ratio derived from isocyanate group of organic diisocyanate>
First, the total nitrogen content in the thermoplastic polyurethane was calculated by elemental analysis under the following conditions.
-Device: Perkin-Elmer Fully Automatic Elemental Analyzer 2400 Series II (standard equipped with autosampler) C · H · N · S / O analyzer · Electric furnace temperature: 975 ° C
・ Sample amount: 2 mg
-Flame retardant: None-Sample container: Tin foil (with flame retardant effect, use 1 sheet)
· Standard substance for preparation of calibration curve: Sulfanylamide Next, nitrogen atom derived from isocyanate group of organic diisocyanate in thermoplastic polyurethane A and nitrogen atom derived from chain extender were respectively detected by NMR measurement under the following conditions .
・ Apparatus: Nuclear magnetic resonance system made by Nippon Denshi Lambda 500
・ Measurement condition: Resonant frequency; 1H 500MHz / probe; TH5FG2
Solvent: DMSO-d6 concentration; 5 wt% / vol
・ Measurement temperature: 80 ° C
・ Number of accumulation: 64s
And the nitrogen content rate originating in the isocyanate group of organic diisocyanate was computed from the result of elemental analysis and NMR.

Differential Scanning Calorimetry (DSC) Measurement
The crystallization enthalpy (ΔH) was determined from the endothermic peak temperature (° C.) of the thermoplastic polyurethane A and the endothermic peak area at the endothermic peak using a differential scanning calorimeter (“DSC 30” manufactured by Mettler, Inc.). The measurement conditions were about 10 mg of sample and a nitrogen gas atmosphere at a temperature rising rate of 10 ° C./min.

<Contact angle with water>
Thermoplastic polyurethane A was sandwiched between two metal plates, and hot pressed using a hot press molding machine (test press for tabletop manufactured by Shinto Kogyo Co., Ltd.). The hot press molding was performed by preheating at a heating temperature of 230 ° C. for 2 minutes and pressing at a predetermined pressing pressure for 1 minute. Then, the two metal plates interposing the thermoplastic polyurethane A were taken out from the heat press molding machine and cooled to obtain a press-formed sheet with a thickness of 300 μm. Then, the obtained press-formed sheet was dried in a vacuum dryer at 60 ° C. for 16 hours. Then, the contact angle of the press-formed sheet with water was measured using DropMaster 500 manufactured by Kyowa Interface Science Co., Ltd.

<density>
A press-formed sheet having a thickness of 2 mm was prepared, and the density was measured in accordance with JIS K7112.

<hardness>
A press-formed sheet having a thickness of 2 mm was prepared, and the hardness (JIS-D hardness) was measured in accordance with JIS K 7311.

<Tensile elastic modulus at 50 ° C. when saturated swelling with water at 50 ° C.>
A 300 μm thick press-formed sheet was produced. Then, a No. 2 test piece (JIS K 7113) was punched out of a 300 μm thick press-formed sheet. Then, the No. 2 test piece was saturated and swelled with water by immersing it in warm water of 50 ° C. for 48 hours. And after wiping off the moisture of the surface of type 2 test piece taken out from warm water, it stood for 2 minutes at atmospheric temperature 50 ° C. Then, a No. 2 test piece is mounted at a chuck distance of 40 mm on a tensile tester (3367 manufactured by Instron), and after standing for 2 minutes at an atmosphere temperature of 50 ° C., a tensile speed of 500 mm / min, N = 6 The tensile modulus was measured under the conditions.

<Water-saturated swelling retention of storage modulus>
A 300 μm thick press-formed sheet was produced. Then, a test piece of 5.0 × 30 (mm) was cut out from the press-formed sheet, and left for 3 days under conditions of 23 ° C. and 65% RH for conditioning. Then, the storage elastic modulus (B) is measured by measuring the dynamic viscoelastic modulus at 50 ° C. at a frequency of 11 Hz using a test piece using a dynamic viscoelasticity measuring apparatus (DVE Rheospectr Co., Ltd., manufactured by Rheology). I asked.
On the other hand, a test piece prepared in the same manner was saturated and swelled with water by immersing in warm water of 50 ° C. for 48 hours. And after wiping off the moisture of the surface of the test piece taken out from warm water, the storage elastic modulus (A) was determined by measuring the dynamic viscoelastic modulus at 50 ° C. at a frequency of 11 Hz.
Then, the storage modulus of a test piece saturated and swollen with warm water is (A), and the storage modulus of a test piece not saturated and swollen with warm water is (B). The following formula (1): A / B × 100
(A is the storage modulus at 50 ° C. of the test piece saturated and swollen with warm water at 50 ° C., B is the storage elastic modulus at 50 ° C. of the test piece not saturated and swollen with warm water at 50 ° C.) ... (1)
Calculated by

<Formability and polishing characteristics>
A single-screw extruder (screw diameter 90 mm) equipped with a T-die equipped with a filter equipped with a pressure gauge was prepared. Then, pellets of thermoplastic polyurethane A are supplied to a single-screw extruder, discharged from a T-die, and passed through a pair of rolls having a gap distance of 1.8 mm and controlled at 60 to 80 ° C. A 2 mm non-porous thermoplastic polyurethane sheet was obtained. The conditions of the single-screw extruder were set to a feeding cylinder temperature of 215 to 240 ° C and a die temperature of 230 to 240 ° C. And the moldability at this time was evaluated by the following method.

(Formability)
A: No unmelted material was observed at the time of molding, and the pressure gauge did not rise.
B: Unmelted material was observed during molding, but the pressure gauge did not rise.
C: Unmelted was observed at the time of molding, and the pressure gauge rose.

  Then, the surface of the obtained thermoplastic polyurethane sheet was ground to obtain a molded article for an abrasive layer having a thickness of 1.2 mm. Then, grooves having a width of 1 mm and a depth of 1.0 mm were formed concentrically at intervals of 7.5 mm on the main surface to be a polished surface of the molded article for a polishing layer having a thickness of 1.2 mm. In addition, as shown in FIG. 2, a corner portion having a tapered shape in which one side extending toward the polishing surface is cut into an equilateral triangle of 0.6 mm as shown in FIG. 2 is formed at the corner portions on both sides of the concentrically formed groove. did. Then, the abrasive layer molding was cut into a circle having a diameter of 38 cm. Then, a cushioning layer was bonded to the back surface with a double-sided pressure-sensitive adhesive sheet to prepare a multilayer polishing pad. As the cushion layer, "Poron H48" manufactured by Inoac Corporation, which is a foamed polyurethane sheet having a thickness of 0.8 mm, JIS-C hardness of 65, and a porosity of 48% by volume is used. Then, the polishing characteristics of the obtained multilayer polishing pad were evaluated by the following method.

(Change in polishing rate over time)
The multi-layer type polishing pad is fixed on the rotary surface plate of a CMP polishing apparatus (PP0-60S manufactured by Nomura Seisakusho Co., Ltd.), and the pressure is 0.18 MPa and the dresser rotation speed is 110 rpm for 30 minutes using a diamond dresser. The polished surface was ground under the conditions. As the diamond dresser, MEC 100-L manufactured by Mitsubishi Materials Corporation was used.

  Then, an 8-inch silicon wafer having an oxide film surface was polished while the slurry was dropped onto the polishing surface of the multilayer polishing pad. The polishing conditions were as follows: platen rotation number: 50 rpm, head rotation number: 49 rpm, polishing pressure 45 kPa, and polishing time 100 seconds. The slurry used was a polishing slurry SS25 manufactured by Cabot Inc. diluted twice with distilled water. The slurry was fed at a rate of 120 mL / min. And the polishing rate (a) at this time was measured.

  Meanwhile, the multilayer polishing pad was left wet for 24 hours. The polishing rate (b) of the multilayer polishing pad left in a wet state for 24 hours was also measured under the same conditions. Then, as an indicator of the change with time of the polishing rate, the maintenance rate of the polishing rate (b) of the multilayer polishing pad after wetting to the polishing rate (a) of the multilayer polishing pad before wetting ((b) / (a ) × 100 (%) was determined.

(Unevenness of polishing)
The film thickness before and after polishing of the silicon wafer was measured at 49 points in the wafer surface. Then, the polishing rate was determined from the difference in film thickness before and after polishing at each point. And the average value of the polishing rate of 49 points | pieces was made into the polishing rate (R). In addition, the standard deviation (σ) of the polishing speed at 49 points was determined, and the nonuniformity of polishing was determined from “nonuniformity (%) = (σ / R) × 100”. The smaller the nonuniformity value, the better the polishing uniformity.

(Evaluation of burr occurrence)
The multilayer polishing pad was attached to an electric polishing machine (RK-3D type) manufactured by Nidec-Shimpo Co., Ltd. Then, while flowing the slurry at a rate of 150 mL / min, the polishing surface of the polishing pad was ground with a diamond dresser under the conditions of 61 rpm dresser, 60 rpm polishing pad and 2.75 psi dresser for 8 hours. As a diamond dresser, a diamond dresser (diamond particle number # 100) manufactured by Allied Material Co., Ltd. was used. The ground surface after grinding was visually observed, and it was judged as good when no burrs were generated at all, and was judged as negative when burrs were generated.

The results are summarized in Table 1.

Example 2
PTMG 850, polyethylene glycol having a number average molecular weight of 600 (PEG 600), BD, MPD and MDI, PTMG 850: PEG 600: BD: MPD: MDI = 11.4: 7.6: 14.7: 6.4: 59.9 ( The monomer mixed in the ratio of mass ratio was prepared. Then, a monomer was continuously supplied to a twin-screw extruder by a metering pump and continuously melt-polymerized while being kneaded to obtain a polymer. After continuously extruding the strand of the polymer in the molten state continuously discharged from the twin-screw extruder into water, the pellet of thermoplastic polyurethane B was obtained by shredding with a pelletizer.

  Evaluation was performed in the same manner as in Example 1 except that thermoplastic polyurethane B was used instead of thermoplastic polyurethane A. The results are shown in Table 1.

[Example 3]
The monomer which mixed PTMG850, BD, MPD, and MDI in the ratio of PTMG850: BD: MPD: MDI = 10.2: 15.7: 8.8: 65.3 (mass ratio) was prepared. Then, a monomer was continuously supplied to a twin-screw extruder by a metering pump and continuously melt-polymerized while being kneaded to obtain a polymer. After continuously extruding the strand of the polymer in the molten state continuously discharged from the twin-screw extruder into water, the pellet of thermoplastic polyurethane C was obtained by shredding with a pelletizer.

  Evaluation was performed in the same manner as in Example 1 except that thermoplastic polyurethane C was used instead of thermoplastic polyurethane A. The results are shown in Table 1.

Example 4
The monomer which mixed PEG600, BD, MPD, and MDI in the ratio of PEG600: BD: MPD: MDI = 10. 9: 15.3: 8.6: 65.2 (mass ratio) was prepared. Then, a monomer was continuously supplied to a twin-screw extruder by a metering pump and continuously melt-polymerized while being kneaded to obtain a polymer. After continuously extruding the strand of the polymer in the molten state continuously discharged from the twin-screw extruder into water, a pellet of thermoplastic polyurethane D was obtained by shredding with a pelletizer.

  Evaluation was carried out in the same manner as in Example 1 except that thermoplastic polyurethane D was used instead of thermoplastic polyurethane A. The results are shown in Table 1.

[Example 5]
PTMG 850, BD, C6-C6 chain extender 1,6-hexanediol (HD), and MDI, PTMG 850: BD: HD: MDI = 19.0: 14.7: 6.4: 59.9 The monomer mixed in the ratio of (mass ratio) was prepared. Then, a monomer was continuously supplied to a twin-screw extruder by a metering pump and continuously melt-polymerized while being kneaded to obtain a polymer. After continuously extruding the strand of the polymer in the molten state continuously discharged from the twin-screw extruder into water, the pellet of thermoplastic polyurethane E was obtained by shredding with a pelletizer.

  Evaluation was performed in the same manner as in Example 1 except that thermoplastic polyurethane E was used instead of thermoplastic polyurethane A. The results are shown in Table 1.

[Example 6]
PTMG 850, BD, 1,8-octanediol (OD) which is a chain extender of 8 carbon atoms, and MDI, PTMG 850: BD: OD: MDI = 17.3: 14.8: 8.0: 59.9 The monomer mixed in the ratio of (mass ratio) was prepared. Then, a monomer was continuously supplied to a twin-screw extruder by a metering pump and continuously melt-polymerized while being kneaded to obtain a polymer. After continuously extruding the strand of the molten polymer continuously discharged from the twin-screw extruder into water, the pellet of thermoplastic polyurethane F was obtained by shredding with a pelletizer.

  Evaluation was performed in the same manner as in Example 1 except that thermoplastic polyurethane F was used instead of thermoplastic polyurethane A. The results are shown in Table 1.

[Example 7]
PTMG 850, BD, cyclohexane dimethanol (CHDM) which is a chain extender having 8 carbon atoms, and MDI, PTMG 850: BD: CHDM: MDI = 14.4: 14.8: 7.9: 59.9 (mass ratio) The monomer mixed in the ratio of was prepared. Then, a monomer was continuously supplied to a twin-screw extruder by a metering pump and continuously melt-polymerized while being kneaded to obtain a polymer. After continuously extruding a strand of the polymer in a molten state continuously discharged from a twin-screw extruder into water, the pellet of thermoplastic polyurethane G was obtained by shredding with a pelletizer.

  Evaluation was made in the same manner as Example 1 except that thermoplastic polyurethane G was used instead of thermoplastic polyurethane A. The results are shown in Table 1.

[Example 8]
Polypropylene glycol (PPG950) with a number average molecular weight of 950, BD, MPD and MDI are mixed in the ratio of PPG950: BD: MPD: MDI = 18.7: 14.8: 6.5: 59.9 (mass ratio) The thermoplastic resin is continuously supplied by a metering pump to a coaxially rotating twin-screw extruder to carry out continuous melt polymerization, continuously extruding the melt into water in the form of strands and then shredding with a pelletizer. Pellets of polyurethane H were obtained.

  Evaluation was performed in the same manner as in Example 1 except that thermoplastic polyurethane H was used instead of thermoplastic polyurethane A. The results are shown in Table 1.

Comparative Example 1
Prepare a monomer in which polytetramethylene glycol (PTMG650), BD, and MDI of number average molecular weight 650 are mixed in the ratio of PTMG 650: BD: MDI = 18.7: 19.6: 61.7 (mass ratio) did. Then, a monomer was continuously supplied to a twin-screw extruder by a metering pump and continuously melt-polymerized while being kneaded to obtain a polymer. After continuously extruding a strand of the polymer in a molten state continuously discharged from a twin-screw extruder into water, the pellet of thermoplastic polyurethane I was obtained by shredding with a pelletizer.

  Evaluation was made in the same manner as Example 1 except that thermoplastic polyurethane I was used instead of thermoplastic polyurethane A. The results are shown in Table 1.

Comparative Example 2
A single amount in which poly 3-methyl pentanediol adipate (PMPA 500) having a number average molecular weight of 500 (BD), and BD and MDI are mixed in a ratio of PMPA 500: BD: MDI = 25.6: 16.3: 58.1 (mass ratio) I prepared my body. Then, a monomer was continuously supplied to a twin-screw extruder by a metering pump and continuously melt-polymerized while being kneaded to obtain a polymer. After continuously extruding the strand of the polymer in the molten state continuously discharged from the twin-screw extruder into water, a pellet of thermoplastic polyurethane J was obtained by shredding with a pelletizer.

  Evaluation was performed in the same manner as Example 1 except that thermoplastic polyurethane J was used instead of thermoplastic polyurethane A. The results are shown in Table 1.

Comparative Example 3
A unit amount of poly 3-methyl pentanediol adipate (PMPA 1000) with a number average molecular weight of 1000, BD, and MDI mixed in a ratio of PMPA 1000: BD: MDI = 29.7: 16.6: 53.7 (mass ratio) I prepared my body. Then, a monomer was continuously supplied to a twin-screw extruder by a metering pump and continuously melt-polymerized while being kneaded to obtain a polymer. After continuously extruding the strand of the polymer in the molten state continuously discharged from the twin-screw extruder into water, the pellet of thermoplastic polyurethane K was obtained by shredding with a pelletizer.

  Evaluation was performed in the same manner as in Example 1 except that thermoplastic polyurethane K was used instead of thermoplastic polyurethane A. In addition, in the comparative example 3, the taper shape was not formed in the corner part of the both sides of the groove | channel formed concentrically. The results are shown in Table 1.

Comparative Example 4
The monomer which mixed PTMG850, MPD, and MDI in the ratio of PTMG850: MPD: MDI = 13.7: 26.4: 59.9 (mass ratio) was prepared. Then, a monomer was continuously supplied to a twin-screw extruder by a metering pump and continuously melt-polymerized while being kneaded to obtain a polymer. After continuously extruding the strand of the polymer in the molten state continuously discharged from the twin-screw extruder into water, the pellet of the thermoplastic polyurethane L was obtained by shredding with a pelletizer.

  Evaluation was performed in the same manner as in Example 1 except that thermoplastic polyurethane L was used instead of thermoplastic polyurethane A. The results are shown in Table 1.

Comparative Example 5
The PMPA 500, CHDM, and MDI are mixed in a ratio of PMPA 500: CHDM: MDI = 11.8: 30.1: 58.1 (mass ratio), and continuously fed to a twin-screw extruder coaxially rotating by a metering pump. After feeding, continuous melt polymerization was carried out, and the melt was continuously extruded in the form of strands into water, and then chopped with a pelletizer to obtain pellets of thermoplastic polyurethane M.

  In the same manner as in Example 1 except that the thermoplastic polyurethane M was used instead of the thermoplastic polyurethane A, the nitrogen content, the differential scanning calorific value, the contact angle with water, 50 when saturated swelling with water at 50 ° C. The water-saturated swelling retention rate of the tensile modulus of elasticity and the storage modulus in ° C. was evaluated.

  Further, a thermoplastic polyurethane M was sandwiched between two metal plates, and hot press molding was performed to obtain a hot press formed sheet. Then, the heat press-formed sheet is placed in a pressure-resistant container, and carbon dioxide is dissolved for 5 hours under conditions of a temperature of 110 ° C. and a pressure of 7 MPa to form a gas dissolving sheet containing 1.6% by weight (saturated amount) of carbon dioxide. I got Then, after cooling to room temperature, the pressure was set to normal pressure, and the gas dissolving sheet was taken out from the pressure resistant container. Next, the obtained gas-meltable sheet was immersed in silicone oil at 110 ° C. for 3 minutes, taken out, and cooled to room temperature to obtain a polyurethane M foam sheet having a thickness of 2 μm.

  Then, using the obtained foam sheet of polyurethane M, density, hardness, moldability and polishing characteristics were evaluated. In Comparative Example 5, no tapered shape was formed at the corner portions on both sides of the concentrically formed groove. The results are shown in Table 1.

  From the results of Table 1, the following can be seen. The polishing pad obtained in Examples 1 to 8 comprising a molded article of a thermoplastic polyurethane polymerized using a chain extender containing a diol having 4 or less carbon atoms and a diol having 5 or more carbon atoms as a polishing layer is a wafer polisher It was excellent at the time of polishing nonuniformity, and also the change with time of the polishing rate was small, and the formability was also excellent. On the other hand, the polishing pads obtained in Comparative Example 1 and Comparative Example 2 having as a polishing layer a molded article of a thermoplastic polyurethane obtained by polymerizing only BD having 4 carbon atoms alone as a chain extender, have high hardness. Although the polishing uniformity at the time of wafer polishing was excellent, the formability was inferior. Moreover, it is a molding of the thermoplastic polyurethane which superposed | polymerized using only BD having 4 carbons alone as a chain extender, and the nitrogen content ratio derived from the isocyanate group of organic diisocyanate is less than 6.3 in Comparative Example 3 The obtained polishing pad had low hardness and therefore low evenness in polishing, and also had a large change with time in the polishing rate and was also inferior in formability. Moreover, although the polishing pad obtained by the comparative example 4 equipped with the molded object of the thermoplastic polyurethane which superposed | polymerized using only C5 MPD alone as a chain extender as a grinding | polishing layer was excellent in the moldability, Since the hardness was low, the polishing uniformity was low, and the change with time of the polishing rate was large, and the formability was also inferior. In addition, the polishing pad obtained in Comparative Example 5 including the porous foam molded article of thermoplastic polyurethane as the polishing layer had low polishing uniformity due to low hardness.

DESCRIPTION OF SYMBOLS 10 Polishing pad 11 Rotating surface plate 12 Slurry supply nozzle 13 Carrier 14 Pad conditioner 15 Abrasive material 16 Polishing slurry 20 CMP apparatus

Claims (12)

Weight of a monomer including a high molecular weight diol, an organic diisocyanate, a first chain extender containing a diol having 4 or less carbon atoms, and a second chain extender containing a diol having 5 or more carbon atoms And a thermoplastic polyurethane which has a nitrogen content of 6.3 to 7.4% by mass derived from the isocyanate group of the organic diisocyanate,
A non-porous compact for an abrasive layer. The first chain extender is ethylene glycol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 2,3-butanediol, 1,4-butanediol, 2-methyl Containing at least one selected from the group consisting of 1,3-propanediol,
The second chain extender is 1,5-pentanediol, 2,2-dimethylpropane-1,3-diol, 3-methyl 1,5-pentanediol, 1,6-hexanediol, cyclohexanediol, 1 2. At least one selected from the group consisting of 8-octanediol, cyclohexanedimethanol, 1,9-nonanediol, 2-methyl-1, 8-octanediol, and 1,10-decanediol. A molded body for an abrasive layer as described above.   The thermoplastic polyurethane has an endothermic peak by differential scanning calorimetry (DSC) at 185 ° C. or less, and a crystallization enthalpy (ΔH) determined from the endothermic peak area at the endothermic peak is 2 to 15 J / g. The molded object for abrasive layers as described in 1 or 2.   The molded article for an abrasive layer according to any one of claims 1 to 3, comprising the first chain extender and the second chain extender each having a carbon number difference of 2 or more. Density 1.0 g / cm ³ or more, the polishing layer molded body according to any one of claims 1 to 4 is JIS-D hardness of 75 or more.   The molded article for an abrasive layer according to any one of claims 1 to 5, which has a surface having a contact angle with water of 75 degrees or less.   The molded article for an abrasive layer according to any one of claims 1 to 6, wherein the thermoplastic polyurethane has a tensile elastic modulus at 50 ° C of 250 to 1,500 MPa when saturated and swollen with warm water at 50 ° C. The thermoplastic polyurethane has the following formula:
A / B x 100
(A: storage modulus at 50 ° C. when saturated swelling with 50 ° C. warm water, B: storage modulus at 50 ° C. when not saturated swelling with 50 ° C. hot water)
The molded product for an abrasive layer according to any one of claims 1 to 7, wherein the water saturated swelling retention ratio of the storage elastic modulus is calculated to be 55% or more.   The polishing layer according to any one of claims 1 to 8, wherein the high molecular weight diol contains at least one selected from the group consisting of polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and polymethyltetramethylene glycol. Moldings. The abrasive layer molding includes an abrasive surface having a recess,
The abrasive product according to any one of claims 1 to 9, wherein the recess has a tapered corner portion that extends toward the polishing surface.   The polishing pad which contains the molded object for abrasive layers in any one of Claims 1-10 as an abrasive layer.   The polishing pad according to claim 11, wherein a cushion layer having a hardness lower than that of the polishing layer is laminated.